1. Field of the Invention
The present invention relates to a distributed type packet switching system and a method of controlling a flow control execution, and more particularly, to a distributed type packet switching system which is provided with a common bus to connect a plurality of communication control modules, each module communicating with at least one terminal for transmitting and receiving data packets, and to a method for specifying a communication control module to execute flow control between two communication control modules engaged in data communication, depending on their respective processing capability.
2. Description of Related Art
Flow control is a general function in packet switching technology to control the volume of data to be transmitted from the originating side equipment, and it prevents excessive data from being transmitted to the terminating side equipment, Therefore, when congestion has occurred in a packet communication between an originating terminal and a terminating terminal, data transmission from the originating terminal is restricted to reduce the load of the packet communication.
In a distributed type packet switching system, which is provided with a common bus to connect a plurality of communication control modules, each module communicating with at least one terminal for transmitting and receiving data packets, the flow control is executed by either (or both) of communication control module(s) for the originating side or(and) the terminating side. The communication control module that is to execute the flow control is specified when a logical channel for the packet communication between the originating terminal and the terminating terminal is established, and once it has been specified, it does not change until the packet communication is completed.
The flow control execution is usually a burden to the communication control module, and extra processing capacity is needed for a processor in the communication control module to handle this operation. Therefore, when the communication control module itself is experiencing congestion due to handling excessive traffic, the processor in the communication control module easily becomes overloaded if the flow control is a/so executed by this module.
As described above, in the conventional distributed type packet switching system, it is not possible to share the load so as to decrease the burden on the communication control module which is currently executing the flow control, by changing the flow control execution operation to the opposite communication control module when the communication control module which is currently executing the flow control experiences congestion but the opposite communication control module has available capacity for processing. This causes a problem in providing smooth packet transmission by a processor having limited processing capacity, and it may require providing a processor having much higher processing capability or restricting the number of terminals in communication with the communication control module.